'Show in external file explorer' on editor menu more than once for split panels

[csabella]

When in the editor, every time the panel is split, the gears menu adds an additional option for 'Show in external file explorer'.

What steps will reproduce the problem?

1. Open the editor.
2. Click on the gears and see 'Show in external file explorer' is listed once.
3. Split the panel.
4. Check the gears on the new panel. 'Show in external file explorer' is now listed twice.
5. Rinse and repeat. It's added one more time for each split.

What is the expected output? What do you see instead?
I expect the menu option to only be listed once.

Please provide any additional information below
I believe this was introduced with PR #4337. In the EditorStack class in widgets editor.py, the incoming argument of actions is appened to(actions.append(external_fileexp_action)). Since this is a list, the append causes it to be changed in the calling routine (EditorSplitter class). When a new EditorStack is created, the new list with the appended action is sent instead of the original list being sent.

Versions and main components

• Spyder Version: 3.x and 4.0
• Python Version: 3.6.3
• Qt Version:
• PyQt Version:
• Operating system: Ubuntu 16.04

Dependencies

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